wot rpm

[60hpomc]

Hi i have a fresh 1983 60hp 2cyl that has 4 hours on it and has come off another boat previously and has a 11-3/4 by 17 pitch prop and it is now on a 900 pound runabout. The timing is retarded becouse of the break in but it only goes to about 4000 rpm at wot. So does the timing not being advanced all the way affect the wot rpm on just how much power it makes? What pitch prop do you feel would be good? I was thinking a 12X13?
Thanks,
Chris

 

[Silvertip]

Re: wot rpm

Until you get the timing set where it's supposed to be, don't even think about a different prop. When the engine is broken in, then make some wide open throttle runs and note maximum speed and maximum rpm. If the engine is not running in the recommended wot rpm band (5000 - 5500 rpm) then check how high the engine is mounted. If the AV plate is flush with the bottom of the boat or an inch or so higher that's ok. If below the hull, raise the engine. Now check speed and rpm. If it's still not up to the recommended rpm a prop change may be required. HOWEVER, 12x13 is not what you need on a 900 pound boat.

 

[60hpomc]

Re: wot rpm

so you think a 11-3/4X17 is a good size? I checked the plate it is flush with the transom maybe 1/2 inch above. Does timing have a large effect on WOT RPM? If so how much?
Thanks
Chris

 

[60hpomc]

Re: wot rpm

Btt